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Exh

|   | 1. | I      have reviewed this Annual Report on Form 10-K of PDC 2005-A Limited      Partnership: |
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|   | 2. | Based      on my knowledge, this report does not contain any untrue statement of a      material fact or omit to state a material fact necessary to make the      statements made, in light of the circumstances under which such statements      were made, not misleading with respect to the period covered by this      report; |
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|   | 3. | Based      on my knowledge, the financial statements, and other financial information      included in this report, fairly present, in all material respects, the      financial condition, results of operations and cash flows of the      registrant as of, and for, the periods presented in this      report; |
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|   | 4. | As      the registrant’s certifying officer, I am responsible for establishing and      maintaining disclosure controls and procedures (as defined in Exchange Act      Rules 13a-15(e) and 15d-15(e)) and internal control over financial      reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for      the registrant and have: |
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|   | a. | Designed      such disclosure controls and procedures, or caused such disclosure      controls and procedures to be designed under my supervision, to ensure      that material information relating to the registrant is made known to me      by others within those entities, particularly during the period in which      this report is being prepared; |
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|   | b. | Designed      such internal control over financial reporting, or caused such internal      control over financial reporting to be designated under my supervision, to      provide reasonable assurance regarding the reliability of financial      reporting and the preparation of financial restatements for external      purposes in accordance with generally accepted accounting      principles; |
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|   | c. | Evaluated      the effectiveness of the registrant’s disclosure controls and procedures      and presented in this report my conclusions about the effectiveness of the      disclosure controls and procedures, as of the end of the period covered by      this report based on such evaluation;and |
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|   | d. | Disclosed      in this report any change in the registrant’s internal control over      financial reporting that occurred during the registrant’s most recent      fiscal quarter (the registrant’s fourth fiscal quarter in the case of an      annual report) that has materially affected, or is reasonably likely to      materially affect, the registrant’s internal control over financial      reporting; and |
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|   | 5. | As      the registrant’s certifying officer, I have disclosed, based on my most      recent evaluation of internal control over financial reporting, to the      registrant’s auditor and the audit committee of the registrant’s board of      directors (or persons performing the equivalent  functions); |
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|   | a. | All      significant deficiencies and material weaknesses in the design or      operation of internal control over financial reporting which are      reasonably likely to adversely affect the registrant’s ability to record,      process, summarize and report financial information;  and |
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|   | b. | Any      fraud, whether or not material, that involves management or other      employees who have a significant role in the registrant’s internal control      over financial reporting. |
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|   | /s/      Richard W. McCullough                        |   |
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|   | Richard      W. McCullough                            |
|   | Chairman,      Chief Executive Officer, and President |
|   | Petroleum      Development Corporation                |
|   | Managing      GeneralPartner                          |

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